1. Field
The present invention generally relates to a device for optical coherence tomography (OCT) and particularly, to a device, among others as described, for a high resolution tomography of an internal scattering medium based on a collective accumulation of single scattering (CASS) microscopy.
2. Description of Related Art
Recently, a development has been underway for an optical coherence topography (OCT) device having a design simpler than that of a computerized or computed tomography (CT) device or a magnetic resonance imaging (MRI) device and resolution higher than that of an ultrasound imaging device. An OCT device directs low coherence light, which is close to natural light, to a multiple- or multi-scattering material, such as biological tissue, and collects reflected light to obtain a tomographic image of the biological material.
Early OCT devices constructed two-dimensional images based on a point scanning and thus, imaging of a large matter was cumbersome, as an area as large as an image to be obtained had to be scanned. A wide-field OCT device developed as an alternative is an OCT device based on an off-axis holography technique, which directs planar wave signals to a matter and a reference mirror and gives an angle to a reference beam, so as to make the beam obliquely incident to a camera and thereby capture a tomographic image by measuring indirect signals. However, when there is a scattering medium before a target, these devices and techniques create imaging distortion due to multi-scattering within the medium.
FIG. 1 is an actual image of a target captured by an OCT device.
FIG. 2 is an actual image of a target captured by a conventional OCT device, when there is a scattering medium before the target.
As shown in FIG. 1 and FIG. 2, an image captured by an OCT device is generally an image obtained through interference signals between a light reflected from a matter and a light reflected from a reference-beam mirror; thus, only a light from a particular position in an axis-direction of the matter may be selectively covered. However, because of a medium causing much scattering within the matter, noise exists in the image, and it is difficult to verify data of a sample when the noise is strong.
Due to noise in an image captured by an OCT device, an angular compounding OCT device has been developed based on a new technique. An angular compounding OCT device captures an image of a matter by measuring an image per incident angle and cumulatively adding an intensity of the image, while changing the incident angle on the matter. Data on the matter to be obtained does not change with a change in incident angles, but as noise components change randomly, noise is reduced in the accumulated images. As such, enhanced contrast effect may be obtained.
FIG. 3 is an actual image of a target captured by an angular compounding OCT device, when there is a scattering medium before the target.
However, as shown in FIG. 3, when noise intensity is relatively stronger than that of signal to be obtained due to a severity or an extent of multi-scattering, there is a limit as to image construction. For example, optical microscopy suffers from loss of resolving power in the target embedded in thick scattering media due to the dominance of strong multiple-scattered waves over the waves scattered only a single time by the target. A solution is needed to maintain full optical resolution in imaging deep within scattering media.